Method for making dairy product capsules

ABSTRACT

The invention concerns dairy product capsules and the method for making them. The capsules contain a coating including a food polymer, reactive to multivalent ions, inside which is confined a dairy product. The capsules are characterised in that they have a breaking force higher than 0.5 N. The invention is applicable in the food processing industry.

The invention relates to dairy product capsules comprising an envelopeinside which said dairy product is confined, and to a process formanufacturing these capsules.

The coating of yogurt in a dietary polymer (sodium alginate) by thetechnique of dripping yogurt into alginate solution is already known(Japanese patent application in the name of Meiji Milk Prod. Co. Ltd.,published under No. 62-130 645): it is indicated in said document thatspherical capsules (yogurt beads) are thus obtained.

However, the yogurt capsules obtained according to said Japanese patentapplication have many drawbacks which considerably limit theirpossibilities for industrial and commercial exploitation:

it is difficult to coat a fluid dairy product in capsules: all theexamples mentioned in the above-mentioned Japanese patent applicationrecommend using a yogurt whose viscosity is high, greater than 2000mPa·s at 10° C.;

their alginate envelope, which is readily deformable, does not allowtheir spherical shape to be maintained. They are also very fragile; theybreak so easily that their handling, in particular during manufactureand packaging, is made very difficult, if not impossible, at anindustrial scale;

they are subject to the phenomenon of syneresis, i.e. the exudation ofliquid at the surface of the capsule. This phenomenon results in surfaceirregularities, and also creates an environment that is favorable tomicrobial growth, which is detrimental to the storage of the beads.

To overcome these drawbacks, it is proposed, in patent application 62-130 645, to immerse the capsules, as they are formed, into an asepticor antiseptic solution or a sugar solution, and to leave them therein inorder to preserve their spherical shape.

The Inventors thus set themselves the aim of providing strong, stabledairy product capsules which do not need to be immersed in a storagesolution, and which are also found by consumers to have a pleasantmouthfeel, and investigated coating polymers which would allow this aimto be achieved.

They have thus found that the selection of coating polymers on the basisof their breaking force makes it possible to obtain capsules that havethe desired properties.

One subject of the present invention is thus a capsule comprising anenvelope comprising at least one polymer for dietary use, which isreactive with multi-valent ions, inside which is confined a dairyproduct, characterized in that said capsule has a breaking force ofgreater than 0.5 N and preferably between 0.5 N and 1.5 N.

For the purposes of the present invention, the expression “polymer whichis reactive with multivalent ions” means a polymer for dietary use whichcan react chemically with multivalent ions (in the present case, theseare ions which have lost more than one electron) to form a crosslinkednetwork (irreversible chemical crosslinking) in the form of a gel. Inparticular, such polymers comprise guluronic, galacturonic or glucuronicunits, more generally uronic units, allowing the chelation ofmultivalent ions, in particular calcium ions which are present in largeamount in dairy products.

Polymers for dietary use which may be used to prepare capsules inaccordance with the invention include, for example, alginates, gellansand pectins, or mixtures of these polymers.

The capsules in accordance with the invention advantageously comprise atleast 40%, preferably at least 45% and advantageously at least 60%, byweight of dairy product relative to the total weight of the capsule.

The dairy product encapsulated in the polymer envelope for dietary usedescribed above may be a fermented or unfermented dairy product, and maybe chosen in particular from yogurts, drinking yogurts, fermented milks,fromages frais, dessert creams and/or dairy mousses. Its texture may bevery fluid (dairy product such as a drinking yogurt) or viscous (dairyproduct such as a stirred yogurt).

The capsules in accordance with the invention are prepared by placingthe dairy product to be encapsulated in contact with a bath comprising,in aqueous solution, at least one polymer for dietary use which isreactive with multivalent ions as defined above. The capsules formed arethen recovered and may optionally be rinsed and then dried.

Depending on the nature of the dairy product which it is desired toencapsulate, two main variants of the process for preparing the capsulesin accordance with the invention may be carried out.

According to a first variant, the placing in contact is carried out bydripping the dairy product to be encapsulated into the bath of dietarypolymer.

To obtain capsules having the desired properties, the polymer which willbe chosen in this case is one which has, as an aqueous 1% solution, aviscosity (measured at 25° C. and at 60 rpm) of less than 200 mPa·s andpreferably less than 100 mPa·s.

Said polymer is advantageously selected from the group consisting or:

highly gelling alanates with a molecular weight of less than or equal to100 000 (commonly referred to as depolymerized alginates); thesealginates are preferably selected from the group consisting of sodiumalginates and potassium alginates;

weakly acetylated gellans, and

pectins with a degree of esterification of less than or equal to 20.

For the purposes of the present invention, the expression “highlygelling ” means alginates whose guluronic acid content is greater than50%, and the expression “weakly acetylated” means gellans whose maximumdegree of substitution with acetyl groups is 0.03. As regards the degreeof esterification of pectins, this corresponds to the percentage ofgalacturonic units of the pectins which bear a methoxyl group.

By way of example of implementation of this first variant of the processin accordance with the invention, the drops of dairy product may beformed using a rigid tube, the aperture diameter of which governs thediameter of the drops (typically from 2 to 15 mm) and which is located afew centimeters above the bath, for example 5-10 cm above it, the dropheight of the drops being adjusted so that the dairy product fullyenters the bath and so that the drops have a substantially sphericalshape. To do this, the viscosity of the bath should be relatively low,preferably less than 200 mPa·s at 50 rpm.

The dairy product is advantageously at a temperature of from 4 to 10° C.and the bath is at a temperature of from 5 to 50° C. approximately.However, the bath temperature should not exceed 45° C. in the event thatthe dairy product is a yogurt, so as not to degrade the bacteria presentin the yogurt.

The drops of dairy product are maintained in the bath for a time whichis sufficient for a film of gel to form around these drops, by diffusionof the multivalent ions, in particular of the calcium ions present inthe dairy product, this gel film being rigid enough to allow thecapsules thus formed to be handled. The thickness of this gel film istypically from 0.1 to 0.5 mm and is set by the time of immersion in thebath (from 2 to 20 minutes approximately).

According to a second variant, the placing in contact is carried out bycoextruding the dairy product with a solution of said polymer fordietary use. This variant allows the use of polymer solutions of highviscosity for which the technique of dripping the dairy product into thepolymer solution can no longer be used. The viscosity of these solutionsmay be greater than 200 mPa·s.

Any one of the coextrusion techniques that are known per se forencapsulating food products, in particular pasty food products, may beused. By way of example, mention will be made of the techniquesdisclosed in patent DE 3 432 923, in international patent application WO92/14544, in patent DE 2 402 415 or in the book: Microcapsule Processingand Technology, Marcel Dekker, Inc., Ch. 7, 59-63 (1979).

A jacketed tube is used: the dairy product is conveyed in the center,and the solution comprising at least one polymer for dietary use whichis reactive with multivalent ions is conveyed at the periphery. Oncethey leave the inner tube, the drops of dairy product are immediatelyrecovered from the polymer solution and are then introduced into acalcium chloride solution for a time which is sufficient for thegelation reaction to take place and for the envelope of the dairyproduct capsules to be strong enough to allow them to be handled.

The thickness of the envelope depends on the feed rates in the two tubesand on the respective viscosities of the dairy product and of thepolymer solution.

In order to carry out this variant, a polymer solution for dietary usewhose viscosity when it is used is about 1100-1200 mPa·s (measured at25° C. and at 64 s⁻¹) is used, such a solution being runny and coatingand spreading uniformly over the yogurt drop.

The polymer used is a polymer which is reactive with multivalent ions,chosen from highly gelling alginates, gellans and pectins with a degreeof esterification of less than or equal to 20.

Whether the coextrusion technique or the drip technique is used, thepolymer solution also advantageously comprises at least one compoundselected from the group consisting of plasticizers, sugars,multivalent-ion sequestrants and water-retention agents.

The plasticizer is preferably selected from the group consisting ofweakly gelling alginates with a molecular weight of less than or equalto 100000, pectins with a degree of esterification of between 20 and 50,sorbitol, glycerol, maltodextrins and polyols.

The expression “weakly gelling alginates” means alginates whose contentof mannuronic acid, this moiety being unreactive with multivalent ions,is greater than 50%.

In a particularly advantageous manner, the presence of at least oneplasticizer makes it possible to soften the network formed by thepolymer for dietary use with the multivalent ions and thus allows theenvelope to melt more satisfactorily in the mouth when it is consumed.

The plasticizer also prevents contraction of the film of polymer fordietary use which is formed and thus further limits the phenomenon ofsyneresis.

The optional presence of sugar ensures better dispersion of themacromolecules of polymer for dietary use during the preparation of thesolution and allows the density of this solution to be adjusted; inaddition, it modifies the taste of the gel constituting the envelope ofthe capsules.

The presence of a multivalent-ion sequestrant makes it possible to trapthe excess multivalent ions which contribute toward the phenomenon ofsyneresis; the multivalent-ion sequestrant is preferably a calcium-ionsequestrant selected from the group consisting of citrates, phosphates,pyrophosphates and metaphosphates. Non-limiting examples which may bementioned include tetrasodium pyrophosphate (Na₄P₂O₇), sodiumhexametaphosphate (Na₅(PO₃)₆) and sodium citrate (C₃H₄(OH)(COONa)₃). Asa variant, the sequestrant is present in the dairy product rather thanin the polymer solution.

The presence of a water-retention agent makes it possible to limit thesyneresis. Such an agent is preferably selected from the groupconsisting of carob and guar, these compounds being galactomannansextracted from the albumin of legume seeds.

When a water-retention agent is present in the case of capsules formedby the technique of dripping into the bath, said bath is maintained at atemperature which is sufficient to lower its viscosity to a value below200 mPa·s; a suitable temperature is, for example, from 30 to 45° C.

The polymer solution advantageously comprises (expressed as percentagesby weight relative to its total volume):

a) between 0.5% and 5% of polymer for dietary use which is reactive withmultivalent ions;

b) between 0 and 10% of plasticizer;

c) between 0 and 2% of sequestrant; and

d) between 0 and 2% and preferably between 0.4% and 2% ofwater-retention agent.

It may also contain between 0 and 20% of sugar.

According to one preferred embodiment of the process according to theinvention, the step of recovering the capsules formed is followed by atleast one rinsing of said capsules with deionized and/or sugary water,to remove the traces of non-crosslinked polymer remaining at thesurface, thus preventing the reaggregation of the capsules after theyhave been packaged. For example, three successive rinsings may becarried out, followed by draining the capsules appropriately before theyare packaged.

According to another preferred embodiment of the process according tothe invention, the rinsing is followed by a step of drying saidcapsules. Such a drying operation makes it possible to evaporate off thewater which is exuded at the surface of the capsules after they havebeen manufactured, and thus to eliminate any subsequent phenomenon ofsyneresis. It may be carried out, for example, by placing the capsulesin contact with a flow of air for 30 minutes to 5 hours, for example at4° C. (for example in a ventilated refrigerator).

The capsules which may be obtained by one or other of the variants ofthe process described above constitute preferred embodiments of thepresent invention.

The envelope of these capsules advantageously comprises, relative to thetotal dry weight of its various constituents:

a) between 10% and 100% by weight of polymer for dietary use which isreactive with multivalent ions;

b) between 0 and 90%, preferably between 0.5% and 10%, andadvantageously at least 1% by weight of plasticizer;

c) between 0 and 30% by weight of multivalent-ion sequestrant;

d) between 0 and 50% of water-retention agent.

The capsules according to the present invention make it possible inparticular to coat a fluid dairy product, such as a drinking yogurt or afluid dessert cream. In addition, they are not particularly fragile andare thus easy to handle during industrial manufacture. These capsulesmay then be stored without further modification, without the need for astorage solution; they keep their spherical shape, and virtually only asmall amount of syneresis is observed, which does not harm the storage.

In addition, the mouthfeel of the capsules in accordance with theinvention is very pleasant. Unlike the capsules disclosed in Japanesepatent application 62-130 645, the capsules in accordance with theinvention are crunchy and release the yogurt, thus producing a sensationof freshness which consumers find very pleasant.

BRIEF DESCRIPTION OF THE DRAWINGS

In addition to the preceding arrangements, the invention also comprisesother arrangements which will emerge from the description which follows,which refers to examples of implementation of the present invention, andalso to the attached FIGS. 1 and 2 which illustrate, in the form ofcurves representing the force exerted on the capsule (in N) as afunction of the deformation (compression) which said capsule undergoes(in mm), the breaking force of capsules according to the prior art(FIG. 1) and according to the present invention (FIG. 2).

It should be clearly understood, however, that these examples are givensolely by way of illustration of the subject of the invention, of whichthey do not in any way constitute a limitation.

EXAMPLE 1 CHEMICAL COMPOSITION, PHYSICAL AND ORGANOLEPTICCHARACTERISTICS OF VARIOUS CAPSULES ACCORDING TO THE INVENTION, IN THEABSENCE OF PLASTICIZER IN THE ENVELOPE OF SAID CAPSULES

The capsules were manufactured according to the process of dripping intoa bath according to the invention. All the viscosity measurementsindicated below were carried out using a Brookfield RVT visco-meter, ata speed of 50 rpm.

The drops of dairy product, 10 mm in diameter, are formed using a rigidtube placed about 5 cm above the immersion bath, said bath being at atemperature of 25° C. Once formed, and after the immersion timeindicated in Table 1 below, the capsules are recovered and rinsed threetimes with deionized water.

The dairy product used is a fluid yogurt whose viscosity at 10° C.,measured at 64 s⁻¹, is 900 mPa·s. Its temperature, at the time ordripping into the immersion bath, is about 5° C.

The alginate used is highly gelling. It is a sodium alginate which has amolecular weight of about 90000 daltons and a viscosity as an aqueous 1%solution, measured at 60 rpm and at 20° C., of 75 mPa·s, and which issold by the company Nutrasweet Kelco (Monsanto) under the name ManugelGHB, or by tile company SKW Biosystems under the name Satialgine SG80.The pectin used is sold, for example, by the company Hercules under thename Genu Pectin LM5CS. It has high gelling capacity, a degree ofesterification of 10% and a viscosity as an aqueous 4% solution,measured at 50 rpm and at 20° C., of about 100 mPa·s.

Table 1 summarizes, for two capsules (1) and (2), the composition of theimmersion bath (w/v of aqueous solution), the immersion time (min), thepercentage of yogurt encapsulated (total w/w of the capsule) and thepercentage of syneresis, measured by weighing the serum exuded by anamount of 50 to 70 g of capsules after storage for 24 h at 4° C. in aclosed container.

TABLE 1 Capsule Composition of the Immersion % of % No. immersion bathtime (min) yogurt syneresis (1) 1.5% alginate 5 71.1 23.4 10% sugar (2)4% pectin 10 75.3 11.3 5% sugar

Capsules (1) and (2) are not particularly fragile and are crunchy whenconsumed.

EXAMPLE 2 CHEMICAL COMPOSITION, PHYSICAL AND ORGANOLEPTICCHARACTERISTICS OF VARIOUS CAPSULES ACCORDING TO THE INVENTION, APLASTICIZER BEING PRESENT IN THE ENVELOPE OF SAID CAPSULES

The capsules were obtained by the dripping technique as described inExample 1.

The dairy product, the pectin and the alginate are the same as inExample 1. However, the formulations given below comprise, in additionto the alginates and pectins of Example 1, other types of alginates andof pectins that are weakly gelling, referred to as “alginate M” and“pectin LM”.

Alginate M is a sodium alginate with a molecular weight of about 18000daltons, sold by the company Nutrasweet Kelco under the name Manucol LB,Pectin LM (“low methoxyl”), sold by the company Hercules under the nameGenu Pectin LM 105-AS, is a pectin with a 46% degree of esterificationand a 9% degree of amidation.

As regards the glycerol present in capsule (4) (see Table 2), it may beobtained, for example, from the company Louis Francois under thereference “glycerol alimentaire [food-grade glycerol]”.

Table 2 summarizes, for three capsules (3) to (5), the composition ofthe immersion bath (w/v of aqueous solution), the immersion time (min),the percentage of yogurt encapsulated (total w/w of the capsule) and thepercentage of syneresis measured according to the procedure described inExample 1.

TABLE 2 Capsule Composition of the Immersion % of % No. immersion bathtime (min) yogurt syneresis (3) 0.75% alginate 10 60.1 13.0 1.5% pectinLM 10% sugar (4) 1.5% pectin 10 66.9 12.9 0.75% alginate 5% glycerol 5%sugar (6) 1.5% pectin 7 69.7 10.0 0.2% alginate 2.5% alginate M 10%sugar

The capsules are rigid enough to be able to be handled without breaking,capsules (3) and (4) being the most solid. When consumed, capsules (3)and (4) have a good crunchy texture, whereas capsule (5) is softer. The“grape skin” effect is attenuated for all of the capsules (3) to (5),the gel being least perceptible in formulation (5).

EXAMPLE 3 MANUFACTURE OF YOGURT CAPSULES BY COEXTRUSION.

a) Composition of the Polymer Solution

The solution which is used to form the envelope of the capsules has thefollowing composition:

2% w/V of pectin LM 5CS (see Example 1);

0.9% w/V of highly gelling alginate (see Example 1);

0.45% w/V of carob;

5% w/V of sugar.

This solution is used at 20° C., which corresponds to a viscosity of1100-1200 mPa·s (viscosity measured using a Brookfield viscometer at 50rpm).

b) Yogurt Used

A yogurt with a viscosity of 1400 to 1650 mPa·s at 10° C. (viscositymeasured using a Rheomat 108 visco-meter at 64 s⁻¹) is used. During thecoextrusion process presented in this example, the yogurt is used at atemperature of 4 to 6° C.

c) Process Used

The coextruder used to obtain the yogurt capsules presented in thisexample consists of 2 concentric tubes:

the yogurt is conveyed, by means of a peristaltic pump, in the innertube, 4 mm in diameter, at a flow rate of 660 to 1080 g/hour;

the biopolymer solution described above is conveyed, with the aid ofanother peristaltic pump, in the outer tube, 8 mm in diameter andforming a 1 mm gap with the inner tube, at a flow rate of 1200 to 1500g/hour.

The ends of the 2 tubes are not positioned at the same level: the outertube protrudes by about 5 mm relative to the inner tube, to preventobstruction or the spurting exit of the yogurt in contact with thebiopolymer solution.

The yogurt drops are formed at the outlet of the inner tube of thecoextruder, under the effect of gravity. They are instantaneously coatedwith the biopolymer solution coming from the outer tube.

The drops thus preformed fall, by a height of 10 to 12 cm (calculated toobtain spherical beads), into a 2% calcium chloride solution, at roomtemperature. 1 to 2 minutes of immersion in this solution allow thecalcium ions contained in the yogurt and the immersion solution todiffuse into the envelope of the beads and complete the gelation(hardening of the envelope).

The beads are then extracted from the calcium chloride solution using ascreen and are rinsed in 3 successive baths of deionized water, whichmakes it possible to prevent reaggregation of the beads after they havebeen packaged and to rinse off the excess calcium chloride. After thefinal rinsing, the beads are drained and then packaged.

d) Physical and Organoleptic Characteristics of the Beads Obtained byCoextrusion

The beads obtained are 10 to 11 mm in diameter with an envelope 0.7 to1.5 mm thick. They comprise from 40 to 45% yogurt and from 55 to 60% gel(envelope), these percentages being expressed relative to the totalweight of the capsule.

The degree of syneresis measured 48 hours after manufacturing thecapsules is 6 to 10%; it is 10 to 12% after 7 days.

An observation of the capsules after 48 hours reveals that they are notparticularly fragile, are crunchy and do not have a “grape skin” effect.The gel releases the yogurt satisfactorily after the capsule has beenburst.

EXAMPLE 4 COMPARISON OF THE BREAKING STRENGTH OF YOGURT CAPSULESACCORDING TO THE INVENTION AND OF CAPSULES OF THE PRIOR ART.

A uniaxial compression test was carried out in order to measure thebehavior of capsules subjected to a pressure.

The capsules used are, on the one hand, capsules obtained according toExample 2 above, and, on the other hand, capsules of the prior artobtained according to Example 1 of the Japanese patent application inthe name of Meiji Milk Prod. Co. Ltd., published under No. 62-130 645.In both cases, these capsules are 10 mm in diameter.

The uniaxial compression test consists in placing a capsule on ahorizontal flat surface and in compressing it using a horizontal plate,whose diameter is greater than that of the capsule, which movesvertically by pressing on said capsule. This plate is fitted with asensor which measures the force exerted on the capsule at any moment.Such a device is available, for example, from the company AdamelLhomargy under the name DY20. The speed of displacement of the plateused is 200 mm/min.

FIG. 1 represents the behavior of the capsules of the prior art and FIG.2 represents that of the capsules according to the present invention,the compression (in mm) being shown on the x-axes and the force applied(in Newtons) being shown on the y-axes.

For the capsules of the prior art, a substantially linear curve profileis observed, which reflects a gradual crushing of the capsule, whichtakes the shape imposed upon it and therefore does not withstand thecompression. This is a behavior of “liquid” type: a 30% reduction in thediameter of the capsules is observed from 0.3 N, and the capsules thencontinue to be flattened and to be deformed without breaking.

On the other hand, for the capsules prepared according to the presentinvention (FIG. 2), the curve shows an exponential shape, the capsuleswithstanding a pressure of 1 N and being deformed only by about 30%relative to their initial size. Next, if the applied force increases,the curve shows a clean break, which reflects the rupture of thecapsule.

It thus emerges that the capsules according to the invention haveelastic behavior: they greatly withstand deformation up to rupture ofthe envelope. In general, the capsules according to the invention have abreaking force of greater than 0.5 N. Depending on the desiredmouthfeel, this breaking force may range from 0.5 to 1.5 N.

What is claimed is:
 1. A process for manufacturing a capsule comprisingan envelope comprising at least one polymer, inside which is confined adairy product, wherein the capsule has a breaking force of greater than0.5 N, the process comprising the following steps: a) preparing anaqueous solution of at least one polymer suitable for dietary use whichis reactive with multivalent ions, said polymer selected from the groupconsisting of i) highly gelling alginates with a molecular weight ofless than or equal to 100,000, ii) weakly acetylated gellans and iii)pectins with a degree of esterification of less than or equal to 20, andat least one compound selected from the group consisting ofplasticizers, sugars, multivalent-ion sequestrants and water-retentionagents; b) placing the dairy product in contact with said solution; andc) recovering the capsules formed.
 2. The process as claimed in claim 1,wherein said placing in contact is carried out by coextruding said dairyproduct with said solution.
 3. The process as claimed in claim 1,wherein said placing of the dairy product in contact with said solutionis carried out by dripping said dairy product into a bath of saidsolution.
 4. The process is claimed in claim 3, wherein said polymer fordietary use has, as an aqueous 1% solution, a viscosity at 25° C. and at60 rpm of less than 200 mPa·s.
 5. The process as claimed in claim 1,wherein the plasticizer is selected from the group consisting of weaklygelling alginates with a molecular weight of less than or equal to100,000, pectins with a degree of esterification of between 20 and 50,sorbitol, glycerol, maltodextrins and polyols.
 6. The process as claimedin claim 1, wherein the multivalent-ion sequestrant is a calcium-ionsequestrant selected from the group consisting of citrates, phosphates,pyrophosphates and metaphosphates.
 7. The process as claimed in claim 1,wherein, the water-retention agent is selected from the group consistingof carob and guar.
 8. The process as claimed in claim 1, wherein thepolymer solution comprises, expressed as percentages by weight relativeto the total volume of said solution: (a) between 0.5% and 5% of polymersuitable for dietary use which is reactive with multivalent ions; (b)between 0 and 10% of plasticizer; (c) between 0 and 2% of sequestrant;and (d) between 0 and 2% of water-retention agent.
 9. The process asclaimed in claim 1, wherein the step of recovering the capsules formedis followed by at least one rinsing of said capsules with deionizedwater, sugary water, or mixtures thereof.
 10. The process as claimed inclaim 9, wherein the rinsing is followed by a step of drying saidcapsules.